Method for forming tubular plastic articles

ABSTRACT

A method and apparatus are disclosed for injection molding tubular plastic articles around cylindrical core pins at a molding station, for cooling the articles while supported on the core pins, and for then axially stripping the articles from the core pins at an ejection station. The article stripping step is accomplished by a horizontally reciprocable carriage which is selectively moved into and out of vertical alignment with a set of core pins and molded articles positioned at the ejection station. Sectional gripping members on the carriage are radially closable when in alignment with the molded articles, to grasp the articles for their axial removal from the core pins upon the horizontal displacement of the carriage. The stripped articles may be held in a horizontal cantilever position between the gripping members during an operational dwell time for additional cooling subsequent to their removal from the core pins.

BACKGROUND OF THE INVENTION

This invention relates generally to the field of injection moldingplastic articles, such as blowable plastic parisons, around a set ofcylindrical core pins, cooling the articles while on the core pins, andthen stripping the molded articles from the core pins for subsequentprocessing.

The art of forming bottles and containers by blow molding has advancedto the stage where several thousands of such articles can be formed eachhour. This necessarily requires that the blowable parisons from whichthe articles are blown be formed rapidly and inexpensively, either byextrusion or injection molding techniques. In injection moldingprocesses, it therefore becomes important to reduce the overall cycletime and to reduce the tooling expenses. Additionally, it is desirablein many situations that the parisons have a thickness profile tooptimize material usage.

The prior injection molding machines have not provided these overalldesirable features. For example, one prior art injection moldingtechnique utilizes horizontally reciprocable molds including core pinswhich are telescopically inserted into an elongated horizontal moldcavity. This arrangement exhibits several shortcomings, including:first, difficulty in molding tapered parisons with controlled varyingthicknesses; second, relatively high cycle times; and third, expensivetooling, for example, because cam-operated mold sections are needed toform the threaded finish.

SUMMARY OF THE INVENTION

The present invention overcomes these prior shortcomings and problemsthrough an injection molding system which, in the total disclosedcombination, includes a turret rotationally mounted about a verticalaxis and having a plurality of horizontal sets of core pins radiallyextending outwardly from the turret. Several separate stations may belocated along an arcuate path adjacent the turret, includingparticularly an injection molding station and a cooling and parisonejection station.

A pair of horizontally positioned mold sections are provided at theinjection molding station and are relatively movable in the verticaldirection to selectively close around the sets of core pins to formtubular injection molding cavities.

At the ejection station, a horizontally movable carriage is utilized tostrip the molded articles from the core pins after they are swung intoposition by the turret. The horizontally movable carriage includes aplurality of semi-cylindrical sets of gripping surfaces which are formedon radially displaceable ejection blocks to selectively engage anddisengage outer peripheral sections of the molded articles. The carriageitself is reciprocable between two primary positions. In the first ofthese positions, each set of gripping surfaces is radially aligned witha portion of a respective core pin at the ejection station; in thesecond of the positions, the gripping surfaces are horizontallydisplaced from the core pins. Displacement means are carried by thecarriage for selectively closing the gripping sections around the moldedarticles at the first of the primary positions and for selectivelyopening the gripping sections at the second of the primary locations, todisengage the plastic article for ejection.

In an optional operation, the displacement means is operable to open thegripping surfaces after the carriage has remained at the second primarylocation for a dwell period, during which time the parisons are held ina horizontal cantilever position for additional cooling.

In another optional operation, the core pins may be indexed to a coolingstation between the injection molding station and the cooling andejection station. This optional station may include a cool air sourcedirecting a stream of cooling fluid onto the exterior surfaces of thethermoplastic articles to facilitate increased production rates.

In one of its broader aspects, the method includes axially aligning amolded article, such as a blowable tubular parison supported on acantilevered, cylindrical mold surface, with a pair of radially spacedgripping surfaces which are laterally spaced from the cantilevered endof the mold surface and molded article. Then, the gripping surfaces aredisplaced in an essentially single, uninterrupted motion toward thesupported end of the mold surface to a position in radial alignment witha portion of the molded article. During their displacement, the grippingsurfaces are first moved toward the cantilevered end of the moldsurfaces and then past the cantilevered mold surface end in radiallyspaced relationship from the molded article. Thereafter, the grippingsurfaces are radially displaced toward the axis of the cylindrical moldsurface to engage and grip a peripheral portion of the molded article.Finally, the gripping surfaces are laterally displaced in unisoncoaxially of the cylindrical mold surface away from the supported moldend to strip the molded article from the mold surface.

Again, an optional method step includes holding the molded articlebetween the gripping surfaces in an essentially cantilevered positionafter the stripping step to continue cooling the article, and thenradially displacing the gripping surface away from each other todisengage the article.

Accordingly, the present invention provides numerous advantages notfound in the prior art. First, the invention utilizes a verticallymovable injection mold which is partable along the axis of the moldcavities, permitting easy contouring of the parison outer diameter toreduce tooling and costs, in addition to permitting optimized materialdistribution. Second, the overall cycle is designed to maintain aninjected parison on a cooled core pin as long as practical, in order tocool the parison to a non-deformable temperature. Third, an ejectionsystem is provided to remove the molded articles from the core pins, andto optionally hold the molded articles in a cantilevered position duringa portion of the overall operational cycle for further cooling. Further,the overall system enables the rapid production of cooled tubularparisons for later use in high production blow molding operations.

Other advantages and meritorous features of this invention will be morefully appreciated from the following detailed description and theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of the overall injection molding andejection system, with partial cross-sectional illustrations for detail.

FIG. 2 is a top plan view similar to FIG. 1, with partial cross-sectionsillustrating the details of the injection molding station.

FIG. 3 is a side elevational view, illustrating the removal of theinjection molded parisons from the mold cavities.

FIG. 4 is a side elevational detail of the ejection station and thehorizontally reciprocable stripping carriage, taken along plane 4--4 inFIG. 5.

FIG. 5 is a frontal elevational view of the ejection system.

FIGS. 6 and 7 relate to a second embodiment, which includes an optionalcooling station between the injection molding and ejection stations.

FIGS. 8-10 illustrate a preferred embodiment of a core pin, whichincludes an undercut in the enlarged head of the core pin to form thelip on the parison.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS The Embodiment of FIGS.1-5

Referring more particularly to the drawings, FIG. 1 illustrates theoverall molding and ejection system, including an injection machine 10,which supplies plasticized, flowable plastic material to an injectionmold 30 by way of a runner housing 20. A rotatable and verticallymovable turret 50 is interposed between the molding station 30 and acooling and ejection station 70, and includes two sets of diametricallyopposed and radially extending identical core pins 60 and 62, which arerespectively positioned at the molding and ejection stations.

The plasticizer 10 may be of conventional design, such as a plunger-typeor reciprocable screw-type machine, and includes a nozzle 12 which mateswith an injection fitting 22 on the runner housing 20. A main runnerline 23 extends transversely along the length of the runner housing 20to supply flowable plastic material to a plurality of branch runnerlines 24 formed by sprue bushings 25. An injection port 31 at the end ofeach injection mold cavity is axially aligned with the sprue bushings 25to selectively receive plastic material for forming the tubular plasticarticles. The selective opening and closing of the branch runner lines24 is effected by a plurality of pin valves 26, which are commonly movedby conventional means (not shown), such as a hydraulic cylinder andpiston and a common displacement plate. As shown in FIG. 1, the runnerhousing 20 is supported on a base plate 27 of a support 34.Additionally, the runner hosuing may include conventional heatingcartridges (not shown) to maintain the plastic material in a heatedflowable condition.

The injection molds include a lower fixed mold half 35 suitably securedto a fixed lower cavity retainer block 33 which is supported on the base34. An upper mold half 36 is likewise suitably secured to an uppercavity retainer block 37 on upper press platen 38 that is verticallymovable by suitable conventional power means (not shown). The upper andlower mold sections 35 and 36 have semi-cylindrical cavities andsemi-cylindrical ports that collectively form the mold cavities 32 andthe injection portions 31. Optionally, the mold halves may includefinish and neck support contours 39. As shown in FIGS. 1 and 3, the moldhalves may also include semi-cylindrical recesses 40 for receiving asleeve or enlarged boss 63 on each of the core pins for the purpose ofaligning the core pins within the mold cavities.

The rotatable turret 50 includes a vertically movable and rotatablesupport column 51 which is raised and lowered by conventional hydraulicpower means (not shown) and which is rotated by conventional means (notshown), such as a rack and pinion. A pair of mounting blocks 52 and 53are suitable secured to the rotatable turret and each carry a set ofdiametrically opposed cantilevered core pins 60 and 62, which extendradially away from the mounting blocks for selective placement at eitherthe molding station 30 or the cooling and ejection station 70. Thedisclosed turret arrangement includes four illustrated core pins in eachset, but this number may be varied as desired.

As shown in FIG. 2, somewhat conventional fluid delivery ducts 54 areformed in the turret mounting blocks to supply cooling fluid to theinterior of the hollow core pins, to cool the plastic material as soonas it is injected into the mold cavity and then thereafter when themolded article is conveyed by the core pins to the ejection station.Further, FIG. 1 illustrates that the core pins may include a varyingcontour, as shown by frusto-conical tapering region 64 adjacent thefinish and neck support region, for the purpose of varying the wallthickness of the molded parisons. Similarly the mold halves may becontoured to provide a desired wall thickness distribution, since themolds are partible along the axis of the core pins.

FIG. 3 illustrates that the mold sections part along the axis of thecore pins to facilitate the stripping of the molded articles from themolding cavities. Opening of the molds may be effected in a variety ofways, but the preferred embodiment includes first raising the upper mold36 to the position illustrated in FIG. 3. This enables the upper half ofthe molded articles to be initially stripped from only half the moldcavity surface. Thereafter, the turret is raised to the position shownin FIG. 3, stripping the lower half of the molded articles from theother half of the mold cavity surfaces and thereby exposing the articlesto ambient air for an additional cooling effect. With the turret thuspositioned, clearance is provided to rotate the turret about itsvertical axis for swinging the set of cores pins 60 from the moldingstation along an arcuate path to the ejection station 70.

Turning now to the ejection station 70, illustrated in FIGS. 1,4, and 5,four cantilever tie rods 71 extend from a support structure 72 toreceive the cantilever core pins, as best shown in FIG. 4. Areciprocable ejection carriage 80 carried by the tie rods 71 is movedhorizontally by a push rod 81 interconnected with suitable power means(not shown).

The horizontally movable carriage 80 includes two laterally disposedframe members 82 and 83 and two interconnected upper and lowerhorizontal frame members 84 and 85, each having suitable openings toreceive the four tie rods 71. Two vertically aligned hydraulic cylinders86 and 87 are respectively secured to the upper and lower frame members84 and 85, which include vertical bores 88 and 89, respectively, toreceive piston rods 90 and 91 associated with each of the hydrauliccylinders. The ends of the piston rods are rigidly secured to respectivehorizontal ejection blocks 92 and 93, having bores 110, 111, 112, and113 to receive vertical guide rods 94 and 95. As best shown in FIG. 4,the ejection blocks 92 and 93 have several sets of semi-cylindricalgripping surfaces 97 and 98 corresponding in countour to the finish andneck support ledge on the molded article.

When the ejection blocks 92 and 93 are moved toward each other, i.e. ina radially inward direction relative to the axis of the core pins, tothe illustrated position in abutment with blocks 99 and 100, thegripping surfaces 97 and 98 engage and grasp the finish and neck supportregion of the molded articles. Then, as the carriage 80 is moved fromthe position shown in phantom lines in FIG. 4 to the full line positionof FIG. 4, the molded plastic parisons are stripped from the core pins.The ejection blocks 92 and 93 may then be immediately retracted by thehyraulic cylinders 86 and 87 to disengage the parisons to permit them tofall onto a conveyor or into a hopper for further processing.Alternatively, the ejection blocks may remain closed while the turret 50is rotated to position the other set of core pins at the ejectionstation with freshly molded articles, during which time the strippedparisons are held in a horizontal cantilevered position to continuecooling, as illustrated in FIG. 4. During this time, optional coolingair currents may be directed onto the parisons. After rotation of theturret to position another set of core pins at the ejection station andafter the release of the parisons from the ejection blocks, the carriage80 is horizontally displaced back to the phantom-line position shown inFIG. 4 to strip the next set of parisons from the core pins. Normally,the parisons will be stripped from the core pins just prior to indexingthe turret, in order to maintain the parisons on the cooled core pins aslong as practical during the overall cycle.

In the overall operation, one of the sets of core pins is enclosedwithin the mold cavities 32 to receive flowable plastic material fromthe injection molding machine 10 and the runner housing 20. At the sametime, the second set of core pins is positioned at the cooling andejection station 70 between the cantilever tie rods 71. During theinjection molding step, the horizontally displacable carriage 80 ismoved from the position shown in FIG. 4 to a position where the grippingsurfaces are in alignment with the finish and neck support region of theparison. Naturally, the ejection blocks 92 and 93 are in a retractedposition during the horizontal carriage movement toward the turret.After the carriage 80 has been moved into proper alignment with themolded article, the ejection blocks 92 and 93 are moved toward eachother by respective piston rods 90 and 91 of hydraulic cylinders 86 and87 to place gripping surfaces 97 and 98 into engagement with theappropriate portion of the molded parisons. Immediately thereafter, thecarriage 80 is reciprocated back to the position shown in FIG. 4 tostrip the parisons from the core pins. As discussed previously, theejection blocks may be opened promptly to drop the molded parisons;alternately, the ejection blocks may remain closed for a dwell period tohold the parisons in a horizontal cantilever position for continuedcooling as the turret is raised and rotated.

After one set of parisons has been injected onto one set of the corepins and the previously molded set of parisons has been stripped fromthe other set of core pins, the molds are opened, as shown in FIG. 3, sothat the turret may be rotated to repeat the cycle sequentially.

The Embodiment Of FIGS. 6 and 7

FIG. 6 illustrates a second embodiment identical in every respect to thepreviously disclosed embodiment, with the exception that an additionalcooling station 350 is interposed between the injection molding station230 and the ejection and cooling station 270. Accordingly, thevertically raisable and rotationally mounted turret 250 includes threesets of core pins 260 which are sequentially positioned at the threeprocessing stations. Apparatus components in this embodiment which areidentical to corresponding components in the embodiment of FIGS. 1-5 arerepresented by reference numerals which are greater by 200 than thecorresponding reference numerals in the prior embodiment. For example,the plasticizer is indicated by reference numeral 210, the runnerhousing by reference numeral 220, and the ejection mechanism byreference numeral 270.

Referring more particularly to FIG. 7, the cooling station 350 is shownas including a lower plenum housing 360 which is supported on a base362. The housing includes elongated semi-cylindrical surfaces 364 havingports 366 for directing streams of air onto the outer surfaces of theplastic parisons 261. Air is supplied to the interior of the lowerplenum 360 by a supply passageway 368 that is connected with a suitablesource of air under pressure.

An upper, vertically movable plenum housing 370 is substantiallyidentical to the lower plenum housing 360 and includes a plurality ofarcuate, semi-cylindrical surfaces 374 which have passageways 376 toalso direct streams of air from the interior of the upper plenum housing370 onto the external surfaces of parisons 261. Likewise, air underpressure is supplied to the interior of plenum housing 370 by a fluidpassageway 378.

In operation, parisons are injected onto a set of core pins 260 at theinjection molding station 230, while the sections of the molds areclosed around the core pins. Thereafter, the upper press platenassociated with the injection mold is raised and turret 250 is raised toan intermediate position between the upper and lower mold halves. Next,the turret 250 is rotated in a counter clockwise manner to position thefreshly injection molded parisons 261 on the core pins 260 between theupper and lower plenum housings 370 and 360, respectively. During thisindexing phase of the operation, the upper plenum housing 370 will beraised by a rod 380 to a position above that shown in FIG. 7;additionally, the core pins and plastic parisons will be above theposition shown in FIG. 7.

After completion of the rotational indexing movement, turret 250 islowered to position the core pins 260 and injection molded parisons 261in the position shown in FIG. 7. After lowering the turret 250, orsimultaneously with the lowering movement of the turret, the upperplenum housing 370 is downwardly displaced by rod 380 which isinterconnected with a conventional power source, such as a hydraulic ram(not shown), to the position in FIG. 7. While the parisons arepositioned at this location, streams of cooling air are directed throughair delivery ports 366 and 376 onto the parison exterior surfaces forcooling. As discussed in connection with the prior embodiment, theparisons are simultaneously cooled on their interior by cooling fluidwhich is circulated through the interior of the core pins 260.

Next, the upper plenum housing 370 is raised, the turret is raised, andthen the turret is indexed in a counter clockwise direction to displacethe parisons from station 350 to station 270 for further cooling andejection. The operation at station 270 is the same as that disclosed inconnection with the operation at station 70 in the embodiment shown inFIGS. 1-5.

The Embodiment Of FIGS. 8-10

This invention also proposes a core pin design for forming a smoothannular end on the lip of an injection molded tubular article. Thisdesign eliminates a parting line along the annular end of the tubularcavity formed by mating core pin surfaces and surfaces on the sectionsof the injections molds, which form a ridge of material on the annularend surface of the molded product. Such a parting line ridge can beundesirable, for example, on the lip of a parison because this resultsin an undesirable parting line ridge on the lip of the blown article.

Referring to the drawings, FIG. 8 illustrates a core pin 460 assupported in a cantilevered manner from a turret or support 450 andinterposed between the upper and lower injection mold sections. Morespecifically, a lower fixed mold half 435 is suitably secured to a fixedlower cavity retainer block 433 which is supported upon a base in thesame manner as shown in FIG. 1. An upper mold half 436 is likewisesuitably secured to an upper cavity retainer block 437 on an upper pressplaten (not shown) that is vertically movable in the same manner asdiscussed in connection with the embodiment of FIGS. 1-5.

In this embodiment, the core pin 460 includes an enlarged centeringcollar or boss 463 which includes oppositely tapering frusto-conicalsurfaces 510 and 512. The mold half sections 435 and 436 each includecomplementary-shaped surfaces 440, 514, and 516 to respectively engagethe enlarged collar 463 and the frusto-conical tapering surfaces inorder to stabilize and center the core pin 460 during the injectionmolding operation. Further, the mold halves include elongatedsemi-cylindrical molding surfaces 432 to form the exterior surface onthe injection molded parison. Surfaces 432 may optionally includefinish-forming surfaces 439. As shown by both FIGS. 8 and 9, thesemi-cylindrical molding surfaces 432 intersect with frusto-conicalsurface 516 to form a shoulder at 517. As shown in FIG. 9, shoulder 517mates with a corresponding shoulder 518 on the core pin, forming aparting line at an edge between the lip and the side walls of thetubular article, rather than on the annular end of the lip.

In accordance with this aspect of the invention, an undercut groove 520is formed radially inwardly of the frusto-conical tapering surface 512to form a smooth annular end surface for the tubular mold cavity. Inpreferred embodiment, the groove is generally arcuate in order toprovide a rounded, smooth surface on the end of the molded parison, asshown by reference numeral 610 on parison 600 in FIG. 10. Asillustrated, the undercut groove 520 extends from the shoulder 518 andblends into the elongated cylindrical molding surface on the core pin.

It will be apparent to those skilled in the art that the foregoingdisclosure is exemplary in nature rather than limiting, the inventionbeing limited only by the appended claims.

Accordingly, having clearly and completely defined by invention, I nowclaim:
 1. A method of forming an essentially tubular, blowable, plasticparison, by the steps of:(1) surrounding an essentially cylindrical moldsurface with respective closed mold halves at a molding station to forman essentially tubular injection molding cavity; (2) injection moldingan essentially tubular parison around said cylindrical mold surface; (3)cooling the parison while said parison is only interiorally supported bythe mold surface and while displacing the mold surface along an arcuatepath to a position at a stripping station in axial alignment with anaxially reciprocable stripping mechanism including a pair of radiallyspaced gripping surfaces which are closable upon an exterior portion ofthe parison; (4) axially displacing said pair of spaced grippingsurfaces in unison from a position laterally spaced from the parison toa position in lateral alignment with said parison but radially separatedtherefrom; (5) radially inwardly displacing said gripping surfaces inunison to engage and grip an external surface portion of the parison;and then (6) axially displacing said gripping surfaces in unison withthe parison held therebetween to strip the parison from the cylindricalmold surface; (7) supporting said parison in a cantilevered mannerbetween said gripping surfaces for further cooling; and then (8)ejecting said parison by radially outwardly displacing the grippingsurfaces in unison.
 2. In a method of making blowable thermoplasticparisons on a high production basis, the steps of:(1) surrounding afirst set of laterally spaced, essentially cylindrical cores withrespective closed molding surfaces formed by a pair of verticallyaligned, relatively movable mold halves at a molding station to form aplurality of laterally spaced, essentially tubular injection moldingcavities; (2) simultaneously injecting flowable thermoplastic materialinto said plurality of cavities to form an essentially tubular, blowablethermoplastic parison surrounding each of said respective cores; (3)opening the mold halves to expose the injection molding parisons, assupported on the cylindrical cores; (4) displacing said first set ofcores in unison from the molding station along a predetermined arcuatepath to a parison ejection station, while simultaneously displacing asecond set of laterally spaced cores along an arcuate path to themolding station; (5) performing steps (1), (2), and (3) while saidsecond set of cores are at the molding station, and while stripping thetubular parisons from the first set of cores at said ejection station bythe steps of:(a) radially displacing sections of respective grippingsurfaces toward each other to engage a peripheral surface portion ofeach of said parisons; (b) laterally displacing the gripping surfacescoaxially and concentrically of each of the respective cylindricalcores, while engaging said peripheral parison surface portions, to aposition laterally spaced from said cores; and then (c) radiallydisplacing the sections of the respective gripping surfaces away fromeach other to disengage the parisons and permit their removal; and (6)displacing said first and second sets of cores along predeterminedarcuate paths from their respective positions at the ejection andmolding stations to position the first set of cores at the moldingstation to repeat the foregoing steps and to position the second set ofcores at the ejection station for the performance of Steps (5a, b, andc); and (7) performing Step (5c) after the performance of Step (6), tohold said parisons in a cantilevered position for cooling.
 3. In amethod of injection molding parisons around a plurality of horizontalsets of core pins mounted in cantilevered manner on a rotatable andvertically movable indexing turret, the steps of:(1) rotating the turret(a) to position one set of core pins with parisons injection moldedthereon at an ejection station and (b) to position a second set of corepins between upper and lower vertically spaced mold halves at aninjection molding station; (2) lowering the turret (a) to axially alignthe first set of core pins with respective, radially spaced sections ofannular gripping surfaces that are laterally spaced from the freecantilevered end of the parisons and (b) to position the second set ofcore pins within half-sections of a plurality of respective injectionmolding cavities formed in the lower mold half; (3) lowering the uppermold half to completely surround the second set of core pins within aplurality of respective injection molding cavities, and thereafterinjecting flowable plastic material into the mold cavities to formparisons around the second set of core pins; (4) stripping the parisonsfrom said one set of core pins at the ejection station by (a)transversely moving the gripping surface sections toward the turret to aposition into radial alignment with a portion of each respectiveparison, (b) closing the gripping surfaces around respective parisons,(c) transversely moving the gripping surfaces away from the turret to aposition laterally spaced from the free cantilevered end of the corepins, (d) holding the parison in a cantilevered position for furthercooling; and (e) opening the gripping surfaces to release the parisons;(5) raising the upper mold half after the performance of Step (3); and(6) raising the turret after the performance of Steps (4) and (5) toaccommodate its rotary indexing for positioning core pins successivelyat the molding and ejection stations.
 4. The method as defined in claim3, wherein the turret includes a third set of core pins, characterizedin Step (1) by displacing the third set of core pins with respectiveinjection molded articles thereon from the injection molding station toan intermediate cooling station.
 5. A method of forming an essentiallytubular, blowable, plastic parison by the steps of:(1) positioning aparison core pin at an injection station; (2) surrounding the core pinwith respective closed mold halves at said injection station to form atubular injection molding cavity; (3) injection molding an essentiallytubular parison of plastic material around said pin; (4) completelyremoving said mold halves from contact with said parison whereby saidparison is only supported interiorally by said pin; (5) cooling theparison while supported on the pin and displacing the pin along anarcuate path to a position at a cooling station; (6) cooling the parisonfurther while supported on the mold surface and displacing the moldsurface along an arcuate path to a position at a stripping station inaxial alignment with an axially reciprocable stripping mechanismincluding a pair of radially spaced gripping surfaces which are closableupon a portion of said parison; (7) axially displacing said pair ofspaced gripping surfaces in unison from a position laterally spaced fromsaid parison to a position in lateral alignment with said parison butradially separated therefrom; (8) radially inwardly displacing saidgripping surfaces in unison to engage and grip an external surfaceportion of the parison; and (9) axially displacing said grippingsurfaces in unison with said parison held therebetween to strip saidparison from said core pin; (10) holding the parison in a cantileveredposition for further cooling; and then (11) moving the core pin towardthe injection station preparatory to the performance of Steps (1)through (10).